Congress took its first nip at President Carter's new anti-inflation plan yesterday when a House subcommittee voted to roll back a Federal Reserve Board rule allowing creditors to change payment terms on consumer debt on 30 days' notice.

The vote came over objections of Fed Officials after consumer groups charged that the rule would place an unfair burden on those who are paying off debt. However, the bill was supported by White House consumer adviser Esther Peterson.

The developments came as Chase Manhattan Bank, the nation's third largest, reduced its prime lending rate for large corporate customers to 19 percent from 19 1/2 percent. It was the third drop in the prime in the past two weeks.

Meanwhile, Charles L. Schultze, President Carter's chief enconomist, told the Senate Appropriations Committee that all signs now point to the fact that the economy is in a recession, but predicted it will be "mild."

Separately, the Council on Wage and Price Stability, the administration's inflation watchdog agency, declared formally that the new three-year wage settlement negotiated bythe steelworkers union is "in compliance" with the guidelines.

In a written statement, the agency said by its calculations the steelworkers' pact would boost industry wages and fringes by 7.65 percent a year, or 24.7 percent over the life of the contract -- well within the 7.5 percent to 9.5 percent standard.

Industry officials privately have estimated the contract as calling for a 31 percent increase over three years, but the council's computation formula omits the cost of pension improvements and purposedly undercounts cost-of-living increases.

The action by the House Banking Subcommittee would prohibit creditors from changing payment terms on exissting balances and would require them to give consumers 60 days' notice before altering the terms of future credit.

The Fed issued regulations April 2 that would allow credit-card issuers to require faster payment of outstanding debt or stiffen their repayment terms provided they gave 30-days' notice. The agency is trying to tighten credit generally.

Yesterday's legislation, sponsored by subcommittee Chairman Frank Anunzio (D-Ill.), also would remove the current of 5 percent on the size of the discount that merchants may offer buyers who use cash instead of credit. o

Federal Reserve Board Governor Nancy Teeters urged the panel to reject the provision prohibiting creditors from changing payment terms retroactively because it may have "a greater adverse effect on consumers" than the current rule.

The package is scheduled to be considered by the full House Banking Committee next Wednesday. yesterday's legislation won surprise support from the panel's Republicans, as well as from the Democratic majority.

Teeters also told the subcommittee that preliminary data indicate the Fed's restrictive credit policies already are taking effect and consumer credit is declining as policymakers had hoped.

She said because of the Fed's restrictions it now appears that the nation's credit and base will be smaller because issuers are withdrawing some credit cards and are tighteining their standards for granting new ones.

At the same time, the Fed governor expressed concern that individual banks might adopt too stringent a policy on their bank credit cards. She said the Fed didn't intend for banks to restrict the use of their credit cards severely.

Teeters also disclosed that the Fed is predicting the inflation rate, now 18.2 percent will drop to between 9 percent and 13 percent by the end of this year -- in line with recent projections made by the administration.

Chase Manhattan Bank's reduction in the prime rate was described by bank officials as a further reflection of the recent drop in the bank's own cost of obtaining money.

White House consumer adviser Esther Peterson's support of the Anunzio bill appears to pit the pit the administration and the Federal Reserve Board in opposition sides on the new credit rule.

However, a spokesman for Peterson's office said the administration objects ony to the specifics of the particular rule and not to the Fed's overall action in tightening credit.